The widespread availability of personal computers at low cost has lead to a situation where the general public increasingly demands access to the Internet and other computer networks. A similar demand exists for wireless communications in that the public increasingly demands that cellular telephones be available at low cost with ubiquitous coverage.
As a result of their familiarity with these two technologies, the general population now increasingly wishes to not only have access to computer networks, but also wishes to access such networks in wireless fashion as well. This is of particular concern for the users of portable computers, laptop computers, hand-held personal digital assistants (PDAs), and the like, who would prefer and indeed now expect to be able to access such networks with the same convenience they have grown accustom to when using their cellular telephones.
Unfortunately, there is still no widely available satisfactory solution for providing low cost, high speed access to the Internet and other networks using the existing wireless infrastructure which has been built at some expense to support cellular telephony. Indeed, at the present time, the users of wireless modems that operate with the existing cellular telephone network often experience a difficult time when trying to, for example, use the Internet to view web pages. The same frustration level is felt in any situation when attempting perform other tasks that require the transfer of relatively large amounts of data between computers.
This is at least in part due to the architecture of cellular telephone networks, which were originally designed to support voice communications, as compared to the communication protocols in use for the Internet, which were originally optimized for wireline communication. In particular, the protocols used for connecting computers over wireline networks do not lend themselves well to efficient transmission over standard wireless connections.
For example, cellular networks were originally designed to deliver voice grade services, having an information bandwidth of approximately three kilohertz (kHz). While techniques exist for communicating data over such radio channels at rate of 9600 kilo bits per second (kbps), such low frequency channels do not lend themselves directly to transmitting data at rates of 28.8 kbps or even the 56.6 kbps that is now commonly available using inexpensive wireline modems. These rate are presently thought to be the minimum acceptable data rates for Internet access.
This situation is true for advanced digital wireless communication protocols as well, such as Code Division Multiple Access (CDMA). Even though such systems convert input voice information to digital signals, they were also designed to provide communication channels at voice grade bandwidth. As a result, they have been designed to use communication channels that may exhibit a bit error rate (BER) of as high as approximately one in one thousand bits in multipath fading environments. While such a bit error rate is perfectly acceptable for the transmission of voice signals, it becomes cumbersome for most data transmission environments.
Such a high bit error rate is certainly unacceptable for Internet type data transmissions. For example, the Transmission Control Protocol/Internet Protocol (TCP/IP) standard in use for Internet air transmission uses a frame size of 1480 bits. Thus, if a bit error is received in every frame, such as detected by a frame check sequence, it would appear as though every single frame might have to be re-transmitted in certain applications.